The photoionization spectrum of highly excited hydrogen atoms in the energy range
between E = 0 and E = Ec ionization thresholds is examined in the presence of a strong de
electric field. Atomic hydrogen is excited from the ground state via a three-photon process
to high-lying excited states. Detailed experimental studies are made of the various
properties of the resonant structures, and the results are compared to numerical
calculations. It is found that the external electric field can be used to manipulate, control,
and design specific atomic structures. These resonant structures are nearly onedimensional
and whose electronic distributions are highly extended along the field, and
which may have enormous electric dipole moments. Such one-dimensional hydrogen
atoms are ideal tools for studying a number of physical phenomena and applications.